On the durability and interface mechanisms of natural FRC: a material for the sustainable construction industry

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Title: On the durability and interface mechanisms of natural FRC: a material for the sustainable construction industry

Author(s): Flávio de Andrade Silva, João de Almeida Melo Filho, Saulo Rocha Ferreira and Romildo Dias Toledo Filho

Publication: Special Publication

Volume: 299

Issue:

Appears on pages(s): 1-14

Keywords: cement based composites, natural fibers, sisal, durability, interface, microstructure

Date: 1/1/2015

Abstract:
The durability performance and interface transition zone of natural fiber reinforced concrete has always been a major concern. Natural fibers due to its hydrophilic nature present a high volume variation which may cause degradation in the fiber-matrix interface. Furthermore, natural FRC may undergo an enhanced aging process, while submitted to a humid environment during which they may suffer a reduction in ultimate strength and toughness. This paper presents how the use of a matrix with low content of calcium hydroxide can mitigate the embrittlement process of natural fibers. The durability performance of the composite systems is examined and the mechanisms for the significant delay in the fiber degradation when the total amount of calcium hydroxide is reduced from the matrix discussed. Furthermore, it is shown how the repeated wetting and drying cycles affects the fiber-matrix interface. Pull-out tests were performed in sisal fiber cement composite systems to study the mechanisms that influence the fiber-matrix bond. The results showed that the use of a matrix with low amount of calcium hydroxide improved the composite durability and that the wetting and drying process reduced the water absorption capacity of the fiber and increased the fiber-matrix bond.